Multistage centrifugal pump



1953 w. H.|CURT|S ET AL 2, 21

, MULT'ISTAGE CENTRIFUGAL PUMP Filed Feb. 15, 1951 2 Sheets-Sheet l Leslie 1,. Aspelin I dame; Coolidge Carzer Nov. 24, 1953 w. H. CURTIS ET AL MULTISTAGE CENTRIFUGAL PUMP 2 Sheets-Sheet 2 Filed Feb. 15. 1951 A Mi 1571 5 zfzZctz-"s William Curtis Leslie L. Aspelin' Cari-er James Coalidge a Hffqz Patented Nov. 24, 1953 UNITED -JSTATES 20 Claims.

This invention relates to improvements in centrifugal pumps and more particularly relates to improvements in multistage centrifugal pumps particularly adapted to pump jet fuel and the like.

A-principal object of our invention is to provide a novel and eflicient form of multistage centrifugal pump arranged with a view towards automatically delivering a constant volume of fluid.

A further object of our invention is to-provide a new and improved form of multistage fluid pump automatically controlling the discharge volume of the pump by variations in pressure drop across anorifice, from a-predetermined normal constant pressure drop, to attain-a constant pressure drop regardless of variations of flow rateof the pump. v

Still'another object of our invention is to provide a, novel 'form of control means for a multistage centrifugal pump automatically activating or deactivating certain stages of the pump, by variations in pressure drop across an orifice at the discharge side of the pump, from a predetermined constant pressure drop.

Still another object of our invention is to provide a new and improved control means for controlling the discharge pressures of a fluid pump by utilizing pressures on the intake side of the pump to render certain'of the stages of the pumpactiveor inactive and in controllingthe distribution of pressure .to the various stages of the pump by variations in pressure drop across an orifice the discharge side of the pump from a predetermined constant pressure drop.

A further object-of our invention is to provide anew and improved form of multistage centrifugal pump together with means controlled by the pressure drop across an orifice at the discharge side of the pump, for progressively activating or'de-ractivating the stages of the pump as the pressure drop varies from a predetermined normal constant pressure drop.

-A still further and more detailed object of our invention is to provide a new and. improved form of multistage centrifugal pu mp for .jet fuel and the-likehaving a plurality of impellers and associated diffusers forming-the stages of the pump, wherein the activation or de-activation of the several stages of t-hepump is eflected by establishing a pressure diiferential on opposite faces of certain of the diffusers of the ,pump or by bringing .the pressures into equilibrium, and wherein the variation iof pressure differential is controlled by variations in rate of flow of the 2 pump from a predetermined required rate of flow.

Another object of our invention is to provide a multistage centrifugal pump particularly adapted for jet fuel and the like including a plurality of alternately arranged impellers and diffusers together with a control means for progressivelyrenderingthe stages of the pump active or inactive by reducing the pressure against one-faceof certain of the diffusers and thereby creating a differential in pressure on opposite sides thereof to rendersaid diifusers active, and

. by balancing :the pressure on opposite faces of certain of said diffusers to allow said diifusers to freely rotate with said impellers'and become inactive.

In carrying out our invention, we alternately mount a plurality of impellers and difiusers on a powerdriven shaft withina housing and-provide an inlet into said housing communicating with the first of said impellers and an *outlet from said housing communicating with the 'last of said diffusers, and rotatably drive the impellers by :power. We also progressively render the diffusers active or inactive upon variations in rate of flow of the pump from a predetermined constant rate of flow. We further utilize pressure in the intake passageway of the pump, which may be greater or less than atmospheric pressure, to establish a difierential in pressure on opposite faces of the diffusers, causing the diffusers to be .forced against the casing of the pump and 'held from rotation by frictional engagement therewith and become active, and vary the pressure differential, to create a balanced pressure on opposite sides thereof, allowing the diffusers to rotate With the impellers, by the pressure of the fluid directed thereon by .said impellers,,and rendering said diffusers inactive. We further control the creation of. a pressure differential on opposite sides of the diffusers by aservo control means operated by variations in rate of delivery of the pump, and by distributing valve means controlled by the servo control means and'operated by pressure derived from the first stage of thepump, A V A These 'and other objects of ourinvention will appear from time to time. as the following specification proceeds and with reference to the accompanying drawings wherein: V

Figure l is a partial, longitudinal sectional view taken through a pump constructed in adcordancewith our invention and through a 5 v0 control, means thereforcontrolling-the :aclt altion "and deactivation or the several stages of the pump and diagrammatically showing a variable orifice and throttle valve in the discharge pipe from the pump;

Figure 2 is a fra mentary transverse sectional view taken throu h the pump, showing certain details of one of the pump impellers;

Figure 3 is a fragmentary transverse sectional view taken throu h the pump, showing certain details of one of the difiusers;

Figure 4 is a transverse sectional view taken substantially alone: line TV V of Figure 1. and showin certa n details of the fl id conne tions to a diffuser for one stage of the numb, for unbalancing the pressure on opposite sides of the diffuser;

Fi re 5 is a dia rammat c view illustratin a mod fioation in the cont ol for the h m and Fi ure 6 is a dia rammatic. view illustrat ng an ther mo fi ation in he control for t e hump,

Referrin now in art c la to th em od ment of our invention s n n the drawin the ump is sho n as com rising a hfi'l'lQinq I" h ving a c ntral ort on ll of a e'enerallv cylindrical or drum like fo m. w th. an. intake end can I. threaded on one end thereof and a di charee end can l3 thread on th o nos te. end th reof. The end cans l2 and I3 are. suitahlv sea ed. to prevent the leaka e o fl id thereby, as by rin s indicated en a ly bv referen e character I4. A drive s aft I is innrn ed in th int e and the dischar e end caps l2 and 13 of the housing In n q hall hearin s IR and H. The end of the sh ft 15 ed cent th nt ke. end can [2 is internall s lin as in eated 11 referen cha acter Hi. to afford a m ans or rotatablv driv n a d sh t bv an e ternal drivin: means, such as the. en ine. of the a rcraft or a senafrate motor not shown A s tahle seal n means, here n d a ramm ticall sho n as be ng a sylph n -lo s S991 is nrnvi eirl in th and can: I2 an 13. to prevent the 'l a'lr'am 0+ flu d f om within the num n c am e ong the shaft and outside of the ends of the ca in The inta e end can H! has an in t ort 22 formed. therein an ohrrm'i nicat n with the intake. side, of an impeller 93 mo nter! nn th shaft [5 for rotat on the ewith. An in a e ine M is h rein sho n as hein" threade n the intake end ca I2 in commun cat on w th the. t 92. The intake can 12 of the hous n I0 is l kew se sho n as havin an inner wall 25 formed. inte rallv th erewith which sfl'l' stnntiallv nun-Forms to the form of blades 26 of the im eller 23. and confines the fluid to said blades for discharge from the uerinherv of a disk 2 of said im el er.

The disk 21 of the imneller 23 is herein shown as having an inner hub portion 29 nressed on a tapered split bushin 30 on the shaft l5. This bushing serves to secure said im eller to said shaft for rotation therewith. The blades 262B extend from the intake side of the disk 2'! beyond the periphery thereof and are shown as being of a generally spiral form and impel the liquid for dischar e across the peri hery of said disk.

Im ellers 33, 34 and 35, like the impeller 23, are likewise s aced along and mounted on the shaft [5 for rotation therewith on split bushings 36, 31 and 38 respectively, in the same manner the impeller 23 is mounted on said shaft. Diffusers 39. 40, 4| and. 42 are iournaled on the shaft 15 between and in association with the respective impellers 23, 32, 34 and 25 on the discharge sides thereof for free rotation with respect to said shaft. The last of said diffusers is shown as being in communication with a discharge port 44,

formed in the discharge end cap E3 of the housing 10, for the discharge of fluid under pressure therefrom.

The diffuser 62 is shown as having an inclined annular disk it of a generally frusto-conical form adjacent and extending parallel with an inclined face 4? of an annular insert 59 of the central housing ii. Said insert may be a casting suitably mounted within the central cylindrical portion ii of the housing 59, as by pressing. The outer end of said insert abuts the discharge end cap 53. The annular insert 49 also forms a continuation of the discharge port id and conducts fluid discharged from the diffuser Q2 thereto. The insert is also has an annular passageway 53 opening to the inside of the can tral housing ii and having a plurality of angularly spaced passageways or ports 5l-5i opening through face 4? to the adjacent face of the disk 55.

The diffusers ll? and t! like the diffuser 2 have annular disk portions 52 and 52, respectively, conforming to the inclined plane annular surfaces 5 and is of annular inserts 56 and 5?, respectively. The inserts and a? conform generally to the outer margins of the respective impeller blades and diffuser disks and have outwardly opening annular passageways formed therein opening to the inner periphery of the central housing if. Said passageways form arrnular passageways, having ports 59 and 6% opening therefrom through the faces 5 1 and 55 respectively and communicating with the respective diffuser disks 52 and 53 for establishing a differential in pressure on opposite faces of said isks, as will hereinafter more clearly appear as this specification proceeds.

The diffuser 3c is herein shown as being shorter than the diffusers 53, iii and 42 and as having vanes 6363 extending from frusto-conical annular disk B l. Stationary diffusing vanes 6565 are herein shown as being formed integrally with an annular insert (it somewhat similar to the inserts 55 and 51 mounted within the central housing portion H. The stationary diffusing vanes 65 form continuations of the vanes {iii- 53 and assure that the first stage of the pump will always be partially active. The annular insert it extends between the diffuser 39 and impeller 33 and confines liquid to the blades of said impeller and has an advance wall 59 having the disk as recessed therein. Low pressure ports EB-l3 lead through said wall from said disk to an annular passageway ii formed between said insert and the inner periphery of the central housing H and afford a means for reducing the pressure on the face of said disk adjacent the wall 89 and creating a differential in pressure on opposite faces of said disk to render the diffuser 39 active.

The diffusers 39, 43, ii and ii are all of a similar construction with the exception that the diffuser 39 is shorter than the succeeding diffusers, so a description of the diffuser 42 will suffice for a description of all of said diffusers. The diifuser 42 includes the frusto-conical annular disk 65 spaced radially from the shaft 15 at its inner end, and providing a fluid passageway between a hub '13 of said diffuser and the inner periphery of the disk 55. (See Figures 1 and 3.) A plurality of spaced difiuser vanes war are mounted on the disk 46 and hub 13 and extend therefrom towards the associated impeller 35. The diffuser vanes i l-M have opposite faces '55 and 75, which diverge from an impeller 35 rotating at a normal rate of speed and the valve element it! in the position shown in Figure 1, the passageway 50 and ports l-5l will be connected with the intake pipe 2 5. This will create a differential in pressure on opposite sides of the diffuser disk 66 forcing said disk into engagement with the inclined face i! of the annular insert -29 and holding said disk from rotation by the friction between said disk and face. The last stage of the pump will then give its full discharge capacity. If, however, the diffuser s2 is allowed to rotate freely, as when pressure on opposite sides of the disk 46 is equal, it will rotate with the impeller 35 at substantially the same speed of rotation as the impeller, by the impact of the fluid discharged from said impeller with a high tangential velocity against the diffuser vanes. Upon rotation of said diffuser the centrifugal effect thereof will oppose and balance off the pressure generated by the impeller 35, and thus reduce the discharge pressure of the fourth stage of the pump to nearly zero. When this occurs this stage of the pump is deactivated.

The diffuser d2, however, is free to rotate only if the fluid pressure on both sides of the disk ts is equal. Hence, if the passage 59 and ports El-51 are closed from communication with the low pressure of port 5 l 6, fluid will leak to the side of the disk :26 adjacent the inclined face ll! of the insert 49 and the pressures on both sides of said disk will balance. Under this condition the disk 45 and diffuser 42 will freely rotate. If, hov ever, the passage as and ports 5i5i are opened to communication with a low pressure port such as the pressure in the pipe 24 which may be below atmospheric pressure, chamber H9 and hollow inside of the valve element it! through the port H6, the pressure of the fluid in the pump will force the disk it; against the face i? of the casting as and the frictional resistance between said disk and casting will hold the diifuser 62 from rotation. The vanes of said diffuser will then act as now straighteners and direct the fluid into the discharge port M and the last stage of the pump will be fully activated.

If, however, pressure in the passageway Eli and ports 5i5l should only be partially released, the pressure differential across the disk it will be less than that required to fully prevent .rotation of said disk and diffuser. Said diffuser will rotate at a slower rate of speed than that of the impeller 3%. This will result in a reduced discharge prcssure for this stage of the pump. It will thus be apparent that the discharge pressure of each of the several stages of the pump is a direct function of the pressure differential across the diffuser disks.

In considering now the operation of all of the stages of the pump and the control means therefor, it should be recalled that the first stage of the pump never completely deactivated by reason of the fact that the vanes 85-55 are always stationary and will serve to partially rcdirect the fluid delivered by the impeller 23, even when the inner diffuser vanes of the diffuser 39 are free to rotate. This assures that there will always be a discharge pressure from the first stage of the pump to activate the servo-controls,

to control the discharge pressure of all of the stages of the pump.

As illustrated in Figure l of the drawings the valve element IE3? is positioned to exert pressure in the passageway 50 and ports 5l5l through the pipe I20, annular port I I hollow interior of force of the spring 81.

the valve element I01 and ports I25 and I I2 communicating with the suction or intake pipe 24. With the valve cylinder H11 in this position, the discharge pressure in the port 44 and pipe 8: will be that due to the partial activation of the first stage of the pump due to the stationary vanes 65, and the full activation of the last stage of the pump. The diffusers 39, 40 and ii will then be free to rotate, rendering the second and third stages of the pump inactive, and the first stage of the pump partially active.

With the pump operating under these conditions, assume that the orifice is variable and controlled by an external source, such as an engine governor 30c, and assume a downward drift of engine speed calling for more fuel. The governor in response to the reduced engine speed will cause the area of orifice a to increase. The pressure drop across the orifice 80a will then decrease and be less than the value required to balance the This will unbalance the forces acting on opposite ends of the valve piston causing said valve piston 55 to move to the right. This will open the port 9? to supply fluid under pressure to the left hand end of the valve element 101, the port I00 and the pipe NH. The right hand port Will also 'be opened to supply pressure at the pressure of fluid in the intake pipe 24 on the right hand end of the valve cylinder I01, through the port I05 and pipe I85. Since pressure in the intake pipe 24 is always less than the discharge pressure of the first stage of the pump, the valve element It! will move to the right. The port 123 will then register with the annular port H5, and the ports 6@89 will be connected with the intake pipe 24 through the pipe H9. A pressure differential will thus be set up across opposite faces of the disk 53 of the diffuser ll, with the result that said diffuser will come into frictional engagement with the inclined face 55 of the insert 51 and will stop its rotational movement and activate the third stage of the pump.

If the discharge pressure of the pump resulting from the activation of the fourth and third stages and partial activation of the first stage is still insufiicient to bring the pressure drop across the orifice 80a, to the predetermined constant value, the piston 85 will remain in its right hand position and the valve cylinder It! will continue to move toward the right and bring the port I22 into registry with the annular port H t, thereby reducing pressure in the ports 59--59 and establishing a differential in pressure on opposite faces of the disk 52 of the diffuser 50, rendering said diffuser active in the hereinbefore described manner.

This process will continue until the rate of fluid flow in pipe BI is sufficient to establish the predetermined pressure drop across orifice til-1. now enlarged, or until the valve element 19'! brings the port it! into registry with the annular port H3 and connects the ports 'Hili with the intake 24, thereby stopping rotation of the diffuser 39 and completely activating the first stage of the pump.

Since the pump is driven from the engine of the aircraft the pump speed will also have drifted downward in the same proportion as engine speed, so the reactivation of pumping stages must continue until the effect of their reduced pump speed has also been overcome.

It should here be noted that the pump is so designed that it should never be necessary to fully activate all of the stages, to deliver the reingj' to thef1restoration ofengine: speed 11011175 origg- 1o 7 inal; preset value. This additional volume of fuel, however, must pass through the fuel-nozzlesK-not: shown) for the engine 1 and, sinceqtheseynozzles mainly have the characteristics t, fixed .orifices;

sail increased. volume of fuel, canonlyibe obtained;

by: an; increasedvdischarge DIGSSUI'GjfIOIll; thepump; Therefore; additional pumping} stage aerr tivatiomwill continue until the discharge=pressureq. has {b68111 reached which; will produce: the, nor-mal fuel nozzles; required. to mestore. the pressure: drop acrossithe lorificecdfia to its predetermined value; 7 Atqthifirpoint the forces acting, on: opposite ends; of; the 1 pistonvalve to "will; have ireturnedi lite to;

its; ;normalgcentral position; and. the piston will;

aga ,be:,in equilibrium;

nzthe vent ft n: upward drift in engine-.-; speeddhe cross sectional area of the 'orificezfiflae will e;.reduce,d, ;and the pressure droniacrosssaidii OIifiCElr-Will; change so: that it: ,exceeds.;the 1318.1;

determined: normal; value; Then; the-.epressw'ea acting upon the right hand end of the valveilii will exoeedi the combined-dorsaof; the spring .187

and heqpressure: of; fiuid=;,acting on;- thfidefl handc end move"; towards the left: Pressure froml the? piper: '5z dsthe rst stage-wotlthegpumpywill thenlbej xertediongthearight; handendof. the-valve cyline dcr Ill? through the pipe lflficandl a-.;.reduced:.

pres rewillibeexerted= on theleft hand .end of 40 saidgyalue' cylinden through the: pine: l 0. I]; I The VBJLVQICY'I-il'l-QQIE"! W1 will-then move to: the left-and: progressively de-activate the stages of thQ IlumDY starting with the first stagevif;saidistagehasz been activated, andrsuccessivelyclosingoneor more of 45.

the respective annular ports M3,; H4, H'EpaIId H 6:- in the a order. named, with the de-activatiomofthe pumping; stages; until. equilibriumis reached.

It should herebeqnoted that the areaaof; the '5().

portopenings of. the valve element It)? issuch that movement of said valve. element alonglthe: valve chamber; its ineither direction, progres-- sively; opens and closes the ports l 13; I Hl,.l l5 and H6, resultingin aeprogressive.activation and deactivationgof the.,.various:stages of-the pump.

It will further be understood that-the coefiicient otirictionbetween thedisks 54, 52:, 53 andfifiof; therespective diffusers ratt e! and .42; may be varied by; the use of suitable, frictionrmateria-lsi to varythe braking. efiect (1116117011118 frictional engagement between the parts. The maintaining otia small amount; of: fluid leakage. aroundthe. respective diffuser disks; from the; pumping-.5

chambers; tov the ports or passageways 1o, 59-, .60 (id and 5! may vary the braking. efiect betweenthe diffusers and stationary parts of the casing. This will,,of. course, be dependent upon theareaof. port openings in the valve I03. Thus by suit-;

ably contouring the opening edges of the ports IZL 22, M3,, and ,l2 i in the valve elementv lll'l, the rateof frictional engagement and braking efiectof the diffusers, dependingupon the coeffie cientiof frictionithereof, may be builtup rela-- tively; rapidly-or gradually and-may ;be haltedosaid valve. The valve. piston; 85 .will then: 135

atany point. Theiactivation as well. asthe-delactivatiom oianyi stage can... thus. be .caused. to. take place atgany desiredrate and-whereit. takes. place: gradually; it. the predetermined pressure drop acrossthe: restriction is reached during a period of transition, the particular stagein which the transition takes-place;Williremain only partially activated, until. aachangein pressure. drop.- occurs.

It may thus be-seen that since the activation .7

and deactiVatiQnof-thevarious stagesis under. fluid controland is attained by the creation ofladifferential. in pressure acrossthe difiuser disks or: by the balancing; of pressure onopposite sides. thereof, thatthe activation and. deactivation of.

the. various. stages of. the pump may be progress sive and-gradual; resulting, in a. gradualincrease) or. decrease in pump pressures controlled-- solelyby. the variationsiinpressure drop, across.

the orifice 8510i, from a predetermined constant. pressure drop.

lfteferring now: to Figure. .5, diagrammatically showing the orifice: a asbeingnxed. andshow.-

ingathrottle cvalvez tl'ile mountedin the pipe 8| downstream of. theiorificetea, and assuming. the pump. is driven. from theengineof the aircraft and thus varies; in speediin. accordance withthe speed; of the enginea, constant dischargeivolume within narrow. limits .may. be attainedthroughout the designed! range .of pumpspeeds" and discharge pressures, which will: dependisolea ly upon thearea of. the-fixed orifice 8ectaand. the

force imposed upon therpistoncvalve ilo .bythe spring 81:.

With. the pumpygin normal operation at normal speed todehverthe desired discharge volume; and with the throttle. valve We.in-osomeflmidposition,

further. closing ofzlsaidi valvezwill result-ima reducedrateof flow. in; the. pipe Bl and through,

the orifice 86a, resulting in; a-reduction ofthe predetermined: pressure .drop across the orifice.

80a, to abelow normaladropi Thisreductionini. pressure a drop Will' unbalance the forces acting upon oppositecends of. thetpiston-valve Bdandl will causessaidpiston valveto move-to -the-rig=hte This will activate additional stages of the pump in r the; manner; previously; y described; a and? will raise. the discharge pressure in-rthespipe -i t until: theirate: not. flow required I to produceathe-=-prede--- termined- -.pressure.:= drop across: the orifice .Sllw shallhave-:- been. reached-.11. Atvthisrpointzvthezuna balancedforces acting-i on: opposite sends of the piston;valve.:-=Wi-llibe iIIBQUlHbFiUm and said.- pistone valvea ills-be inr-its-i: normals mid position: Openingaofr the throttle;.-valveiiile beyond. the.

aforementioned :mid iposition -willr allow! an increase-,in-voluma oi.- fiuid to. pass through: said valve, resulting; inianiincreasedivelocityithrough;o

thesorificeilua-zandia greater than normal pressure, drop acrossssaid. orifices; When. this;.condi.-. tion .4 arises the sunbalancedi forces; aetingsupon.

opposite: ends-.ofz the piston: valve 65 will cause it to move to the left. This will result inithemlewactivationzottthet pumping"; stageseunti-l theedischarge'pressurel-intheepipe 8t shallzhave reachedir the; value? necessarya-to.-.produce1the .-rate -.ot fiow through: theimorificefl iltwzrequired-ato attainothen; predetermined pressure .drop across: the aorificex Whenthis pressure drop oissattained v the; unbalanceda-foroes; acting -upon-roppositeends: of. the piston -:va-lve diewill 1, besin'; equilibrium and sai-clr: piston; valve: zwillireturrr-to its. normal midpo sition-il It.) is obvioussthat a downward adrift-in I pump. speed -.w-i-t-h\ no ichangain thea throttle .opening-,-

will result in reactivation of the pumping stages by the same sequence of events previously described, and that in a contrary manner, an upward drift of pumping speed will bring about deactivating of the pumping stages by the sequence of events previously described.

In the form of our invention shown in Fig. 6, illustrating a modified form in which our invention maybe embodied, the restriction to and orifice 88a have been removed from the pipe Si. A pipe Bla is shown, which instead of being connected with the fuel nozzles like the pipe 8i, may be connected to a hydraulic load, such as a hydraulic motor (not shown) which requires variable volume of supply at constant pressure over and above the pump inlet pressure. In this form of our invention, the control of the pump is attained by the difference between inlet and discharge pressures, to obtain a constant pressure rise across the pump. The pipe 83 is shown as being eliminated and the left hand end of the valve casing 8 is connected to the suction pipe 24 through a pipe 529 and a pipe 1%. The pipe I29 is shown as having an extension 53! leading to the atmosphere for purposes which will hereinafter more clearly appear as the specification proceeds. A valve I32 is provided in the extension l3: to maintain said extension closed. A valve N33 is likewise provided in the pipe i3d to disconnect the lefthand end of the valve body 83 from the intake pipe is when desired, for purposes which will hereinafter more clearly appear as this specification proceeds.

Assuming that the lefthand end of the valve body 8 is connected to the intake pipe 2i and that the valve E32 is closed, and the valve I33 is open, a reduced pressure is maintained on the lefthand end of the valve piston 85 in accordance with the intake pressure of the pump and the force exerted by the spring 87. In this form of our invention the spring 31 may be designed to exert sufiicient force upon the lefthand end of the piston valve 85 to require the full predetermined pressure rise across the pump, to move said piston valve to the left against the force exerted by said spring.

With this arrangement any increase in volume demanded by the hydraulic load, or any decrease in pump speed will, by reason of lowering the pressure rise across the pump, unbalance the forces acting upon the opposite ends of the piston valve 85, causing said piston valve to move to the right and progressively activate the various stages of the pump until the pump produce the demanded volume at the required pressure.

If, however, the hydraulic load demand is for a reduced volume, or if the pump speed has drifted upward, the forces acting upon the ends of the piston valve 85 will be unbalanced in a contrary manner and the piston valve 85 will move to the left, causing the various stages of the pum to be deactivated until an equilibrium is reached.

Assuming now that the valve I33 is closed and the valve l32 is open. The lefthand end of the valve body 84 will then be open to the atmosphere. The spring 81 may be selected according to the gauge pressure desired. Upon any increase in volume demanded by the hydraulic load, or upon any decrease in pump speed, which results in a lowering of the pressure rise across the pump, the forces acting upon the opposite ends of the piston valve 35 will be unbalanced, causing said piston valve to move to the right and activating additional stages of the pum to i2 produce the demanded volume at the predetermined pressure in the manner hereinbefore described.

Where the hydraulic load demand is for reduced volume of fluid, or where the pump speed has drifted upward, the forces acting upon the opposite ends of the piston valve will again be unbalanced so as to cause said piston valve to move to the left resulting in the deactivation of the additional stages of the pump until the delivery volume of the pump is reduced to the hydraulic demand.

It should be noted that in the form of our invention illustrated in Fig. 5 various springs may be substituted for the spring 81 to exert the required force on the lefthand end of the piston valve 85, to attain the required pressure rise across the pump, and that said spring may be adjustable from the exterior of the valve block, to adjust the pressure exerted by the spring to the pressure desired, or to the hydraulic volume demand. Said spring may be adjusted by any one of a number of well known methods operable from the exterior of the valve block which are no part of our present invention so are not herein shown or described in detail. The discharge pressure of the pump above the inlet pressure, or above atmospheric pressure, as the case may be, may then be adjustable within the predetermined range for the pumping unit between the stage of complete activation and complete deactivation.

It should further be understood that the valve assembly and body 84 may be completely eliminated and that the movement of the multiple ported valve element I01 may be controlled directly by manual means, or by any other well known means to accomplish the desired pressure and volume control. 7

It Will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. In a constant delivery volume fluid pump, a housing, an inlet into said housing, an outlet therefrom, a shaft journaled therein, means for rotating said shaft, an impeller on said shaft in communication with said inlet, a diffuser journaled on said shaft for free rotation with respect thereto and including a rotatable disk having a plurality of diffusing vanes extending therefrom, a stationary housing portion extending along one side of said disk, fluid pressure passageways from said housing portion to said disk, and fluid pressure means controlled by the delivery flow of said pump and operable to reduce the pressure in said passageways and establish a differential in pressure on opposite faces of said disk and cause the pressure of the fluid within said pump to force said disk against said housing portion, holding said disk and diffuser from rotation, rendering the diffuser active, and also operable to equalize the pressure on opposite face of said disk and allow said disk to freely rotate on said shaft, rendering said difiuser inactive.

2. In a fluid pump, a housing, an inlet into said housing, an outlet therefrom, a shaft journaled therein, means for rotating said shaft, an impeller on said shaft in communication with said inlet, a diffuser freely journaled on said shaft in communication with said impeller, said housing having a wall portion extending adjacent the opposite face of said diffuser from said impeller, a fluid passageway in said wall portion, a fluid sewerage.

connection-from saidinlet"toasaidi-passageway to;:

reduce the pressure-on the'face oflsaid'M-difiusen' adjacent said wall portion, enabling the fluid,

pressure connections from said dischargeloutletl to operate said. valve means-upon variationsin flow inrsaid outlet from a predetermined. normalv 7 flow.

3 A constant delivery volume fluidpumplcom,

prising a housing, an inlet, intolone end-thereof; an outlet from the oppositeendthereof; apow-er. driven shaft-journaled therein, anlimpeller on. said shaft in communication. with said-inlet. a

diffuser freely journaled on said shaft in communication with':.said impeller and outlet, said housing having a wall portion-extendin alonga face of said diffuser oppositefrom said-impel: let, a passageway leading-through said wall portion to said diff-user, a fluid connectionfromsaid: inlet to said passageway having fluid pressure operated valve means therein, a restricted orifice:

in'said outlet, and fluid pressure connections from opposite sides of said orifice to said valve means, to operate said valve means upon changesin pressure drop across said orifice' from-apredetermined constant pressure drop, to establish a pressure differential on opposite faces of said diff-user renderingsaiddiffuser active, or to balance the pressure on opposite faces of said diffuser, allowingsaid diifuserto freely-rotatewith respect to said shaft.

4. A constant volume fluid pump comprising a housing, an. inlet thereinto, an-outlet therefrom, a shaft journaled therein, an impeller on said shaft, a diffuser associatedwith said inipeller andfreely journaledon said shaft, said housing having a wall portion extending" along the face of said diffuser opposite from said impeller and-having apassageway leading therethrough, a restricted orifice in said outlet, and fluid pressure oonrol means automatically operable upon vari ations in.v pressure drop across said orifice, to activate or render said diffuser inactive comprising a fluid connection from'said inlet to said passageway having afluid pressure operated valve therein, a second" fluid pressure operated valve,-

fluid pressure connections from opposite sides of said restricted -orifice'to-H opposite ends of said second valve for operating. said valve, and-fluid pressure connections fromsaid second valve toopposite endsof said distributor valve for operating said'valve to reduce-pressure onthe side. of said diffuser adjacent said wall-portion.

5. A multistage fluid pump comprising a housing, an inlet thereinto, an outlet-therefrom, a shaft journaledin said housing, a plurality of alternatelyarranged impellers and. diffusers thereon, each impeller and associated diffuser forming astage of the pump said' housing havdriven;- therebm a plurality; of. difiusersvfreelv mountedron. .saidshaft between. said impellers.

eachassociated impeller and diffuser forminga stageofthepumnthe first of said diffusers being; of azlcssen diameter, than, the remaining, diffusers; and saidhousinghavinga plurality of. stationary difiuser .Vanes'in. communication with thevanes of saidxfirsti. diffuser, assuring partial activation ofthe. first; stage of. the pump at all, times, said;

housingahaving' wall portions extending along; the: faces of said. diffusers opposite from said impellerspassageways in. said wall portions, fluid pressureoperated valve meansoperable to afiord fluid communication with said passageways, and

meansroperated by variations in rate of flow from a; requiredwrate of. flow in said outlet to effect! operation; of. said. valve .meansto. progressively afford communication with said passagewaysand progressively-reduce.thepressure in. said passagewaysstartingwith; thelast stage of the pump and" reduce the. pressureon thefaces of said diffusers adjacent saicLwall portions and. hold said diffusersv from.rotationbyxfriotional resistance against said walllportions toactivate said diffusers andv the.

- associated: stages of the pump, and to close said passagewaysfrom fluid. communication and. ao commodate the pressure on opposite sides of said diffusers to balance, and permit. free rotation of saidassociated diffusers and inactivate the associated stages of. the pump;

7. a multistage. fluid :pump, comprising a, housing, an. inlet into. and an outlet from said; housing; a. drive shaft journaledin said housing a plurality ofimpellers spaced along said shaft. and drivenltherebya plurality of diffusers freely; mounted on said shaft between, said impellers, the first of saiddiifusersbeingof a. lesser diameter than the remaining difiusers, and said casing having stationary diffusing vane-s forming a continuation of the vanes of the first of said diffusers, assuring partial activation of the first stage .ofthe .pumpat all times, passageway means in. saidjhousing leading to the faces of said diffusers opposite from said impellers, a. distributor valve, aconnection from said inlet tosaid valve,

and. meanslfor operating said distributor valve totprogressively create a reduction in pressure in, certain, of said passageways starting with. the last of. said diffusers, and establish an unbalanced pressure on opposite faces thereof, pro gre'ssively. rendering said difiusers active or to. progressively block said passageways starting with the firstof said diffusers and balance pressure thereon,. progressively rendering said diffusers inactive.

8. Asmultistage fluid pump comprising a housing, an inlet into and. an outlet from said. housing,.'adrive shaft journaled in said housing, a. pluralityof impellers spaced along said shaft anddriventhereby, a plurality of diffusers freely mounted on said shaft between said impellers, for: free rotationwith respect thereto, the first of said diffusers having a plurality ofvanes and being of a lesser diameter than the remaining diffusers, and. said housing having a plurality of stationary diffusing vanes communicating with said vanesof said first diffuser, and assurin par-. tial activation of thefirst stage'of the p-umpat all times,v said housing alsohaving wall portions, extending. alongthe facesof said diffusers oppo-. site from said impellers, fluid passageways through-said wall; portions, a distributor valve operable. to reduce thev pressure. in said passage-. wayseand; on..the sides. of said. diffusersadjacent said rwallL portions, tohhold said. diffusers from rotation and activate said diffusers by the differential in pressure thereon, and to block said passageways to balance the pressure on opposite sides of said diffusers and permit said diffusers to freely rotate about said shaft, a fluid pressure connection from said inlet to said distributor valve, for creating a reduced pressure therein, a restricted orifice in said outlet, fluid pressure operated valve means operated by variations in pressure across said orifice from a predetermined constant pressure drop, a fluid pressure connection from the first stage of said pump to said last mentioned valve means, and fluid pressure connections from said valve means to said distributor valve to effect operation thereof by pressure derived from the first stage of the pump and the progressive activation or deactivation of the stages of the pump.

9. A multistage centrifugal pump having an inlet and a discharge outlet, a plurality of coaxial impellers and associated rotatable diffusers forming the stages of the pump, means reactin against said diifusers and holding said diffusers from rotation upon an unbalanced pressure thereon, a restricted orifice in said discharge outlet, and fluid operated valve means connected between said inlet and said diffusers and establishing fluid communication therewith from said inlet and operated solely by variations in pressure drop across said orifice from a predetermined constant pressure drop, for unb-alancing the pressure on opposite faces of certain of said diffusers to elfect activation of said diffusers by reaction against said reaction means and render the associated stages of the pump active, and to accommodate the pressure on opposite faces of certain of said diffusers to balance and become active.

10. A multistage centrifugal pump having an inlet, a discharge outlet, a plurality of coaxial impellers and associated rotatable diffusers forming the stages of the pump, means reacting against the opposite sides of said diffusers from said impellers, to hold said diffusers from rotation by frictional engagement therewith, servocontrol means connected with said inlet and said outlet, spring means balancing said servo-control means in accordance with the desired pressure rise across said inlet and said outlet, and valve means connected with said inlet and establishing fluid communication with the sides of said difiusers adjacent said reaction means and operable by said servo-control means for creating a differential in pressure on opposite sides of certain of said diffusers, to accommodate the pressure on the sides of said diffusers adjacent the associated impeller to engage said diffusers with said reaction means and render the associated stage of the pump active, and for accommodating the pressure on opposite sides of certain of said diffusers to come into balance and freely rotate with the associated impellers, rendering the associated stages of the pump inactive.

11. In a varying speed constant delivery volume fluid pump, a housing, an inlet into said housing, an outlet therefrom, a drive shaft journaled therein, an impeller on said shaft, a diffuser at the discharge side of said impeller and journalled on said shaft for free rotation With respect thereto and for limited movement therealong into frictional engagement with said housing, a restricted orifice in said outlet, fluid pressure lines leading from opposite sides of said orifice and fluid pressure operated means connected W th said fluid pressure lines and operated by the difference in pressur on opposite sides of said orifice and having fluid communication with the side of said diffuser adjacent said housing for unbalancing the pressure on opposite sides of said diffuser and accommodating said diffuser to move into frictional engagement with said housing by the unbalanced pressure acting thereon, to activate the pump.

12. In a fluid pump, a housing, an inlet into said housing, an outlet therefrom, a driv shaft journaled therein, an impeller on said shaft in communication with said inlet, a partially activated diffuser including a plurality of stationary diffusing vanes in communication with the discharge of said impeller, and a plurality of rotatable diffusing vanes fornn'ng continuations of said stationary vanes, reaction means extending along one side of said rotatable diffusing vanes and engaged thereby to frictionally hold said vanes from rotation upon unbalanced pressure thereon, a restricted orifice in said outlet, fluid pressure lines leading from opposite sides of said orifice and fluid pressure operated means connected with said fluid pressure lines and operable upon variations in rate of flow in said outlet from a predetermined flow rate and having fluid communication with said rotatable diffusing vanes on the same side thereof as said reaction means, to establish a differential in pressure on opposite sides of said rotatable difiusing vanes and accommodate said vanes to frictionally engage said reaction means and be held from rotation thereby, and render said rotatable diffusing vanes active.

13. In a constant delivery volum fluid pump, a housing, an inlet into said housing, an outlet therefrom, a shaft journaled therein, an impeller on said shaft in communication with said inlet and rotatably driven by said shaft, a partially activated diffuser including a plurality of stationary diffusing vanes in communication with the discharge of said impeller and a plurality of rotatable diffusing vanes journaled on said shaft and forming continuations of said stationary vanes, a stationary member, engaged by said r tatable vanes upon an unbalance of pressure thereon and frictionally holding said vanes from rotation, a restricted orifice in said outlet, and fluid pressure valve means connected between said inlet and said rotatable diffusing vanes and operable by variations in pressure drop across said orifice for establishing communication from said inlet to stationary vanes and unbalance th pressure thereon and accommodate said vanes to engage said reaction means to render said diffuser vanes active, and to balance the pressure on said vanes and accommodate said vanes to freely rotate on said shaft.

14. A multi-stage centrifugal pump having an inlet, a discharge outlet, an impeller shaft, a plurality of coaxial impellers spaced along such shaft and rotatably driven thereby, a separate difiuser in association with each impeller and freely mounted on said shaft, said impellers and associated diffusers forming the stages of the pump, and fluid pressure operated means operable by variations in rate of flow of fluid in said discharge outlet from a predetermined rate of flow to unbalance the pressure on certain of said diffusers and thereby hold said diffusers from rotation and activate the associated stages of the pump, and to balance the pressure on said diffusers and accommodate said diffusers to freely rotate and render the associated stages of the pump inactive, comprising fluid pressure means r, 114 V connected with the opposite faces of said diffusers from the associated impellers, to balancethe pressure thereon, and valve means operable by variations in rat offlow of fluid through said discharge outlet, for supplying or releasing presre m e flu d r sure mean r 15. A multi stage centrifugal pump having an inlet and a discharge Gutlt, an iinpeller shaft, a plurality of coaxial impellers on said impeller shaft and rotatably driven thereby, a stationary diffuser associated with one of said impellers and a plurality of rotatable diffusers freely mounted on said impeller shaft in association with the other of said impellers, and means operable to unbalance the pressure on certain of said rotatable diffusers and thereby effect the holding of said diffusers from rotation and to balance the pressure thereon and accommodate said diffusers for free rotation comprising servo-control means operable by variations in rate of flow in said discharge outlet from a predetermined flow rate, and fluid operated valve means operated by said servocontrol means and connected with said diffusers to relieve fluid pressure from one side thereof and unbalance pressure thereon and progressively activate said diffusers.

16. A multi-stage centrifugal pump havin an inlet and a discharge outlet, a power driven impeller shaft, a plurality of coaxial impellers and associated diffusers on said shaft and forming the stages of the pump, said impellers being secured to said shaft and rotatably driven thereby and said diffusers being freely rotatable on said shaft and being axially movable therealong, and valve means connected with said inlet and establishing communication from said inlet to said diffusers and being operable solely by variations in rate of flow in said discharge outlet from a predetermined constant rate of flow, for unbalancing the pressure on opposite faces of certain of said diffusers to effect the holding of the respective diffusers from rotation and render the associated stages of pump active, and to balance the pressure on opposite faces of certain of said diffusers and effect the free rotation of said diffusers with the associated impellers, and render the associated stages of the pump active.

1'7. In a fluid pump, a housing, an inlet into said housing, an outlet therefrom, a power driven impeller shaft journaled in said housing, an impeller on said shaft and rotated thereby and having fluid communication with said inlet, a partially activated diffuser in communication with said impeller including a plurality of stationary radial diffusing vanes in said housing, associated with and in communication with the discharge of said impeller and rotatable diffusing vanes forming an inward continuation of said stationary vanes and mounted on said shaft for free rotation with respect thereto, a restricted orifice in said outlet, a fluid pressure passageway having fluid communication with the opposite sides of said rotatable diffuser vanes from said impeller, and pressure operated valve means operable by variations in pressure drop across said orifice, to supply fluid pressure to said rotatable diffusing vanes and balance the pressure thereon and accommodate said vanes to freely rotate with said impeller and to unbalance the pressure on said diffusing vanes to effect the holding of said vanes from rotation by the differential in pressure acting thereon, and render said rotatable diffusing vanes active.

18. A multi-stage fluid pump comprising a housing, an inlet into said housing, an outlet from stages of the pump 5,0

housingand having a plurality of alternately arranged impellers and diffusers thereon; each peller being sec uredto said shaft and rotatably ri i b sa h. d f ser em e o ted with an impeller and beingi freely mounted on said shaftiandmeafrs operable to progressively hold said diffusers omrotation and render the v comprising a restricted orific' iii said outlet, servo-control means operable by variations in pressure drop acrosssalid orifice frrn a predetermined pressure drop, valve means operable by said servo coritrol'means, and fluid pressure passagewaysleading from said valve means to the opposite sides or said diffusers from said impellers for releasing presure therefrom and unbalancing pressure thereon, to effect the holding of said diffusers from rotation, and for balancing the pressure thereon to accommodate free rotation of said diffusers.

19. A multi-stage fluid pump comprising a housing having an inlet and outlet, a drive shaft journaled in said housing, a plurality of impellers spaced along said shaft and driven thereby, a plurality of diffusers mounted on said shaft between said impellers for free rotation with respect thereto and for movement therealong, the first of said impellers communicating with said inlet and the last of said diffusers communicating with said outlet, the first of said diffusers being of lesser diameter than the remaining diffusers, said casing having a plurality of stationary vanes therein forming an outward continuation of said first diffuser, assuring partial activation of the first stage of the pump at all times, abutment faces engageable by said diffusers, fluid pressure passageways leading to the sides of said diffusers adjacent said abutment faces, for balancing the pressure thereon and accommodating said diffusers to freely rotate and for unbalancing the pressure thereon to effect engagement of said diffusers With said abutment faces, valve means controlling the passage of fluid under pressure to said fluid pressure passageways, and servocontrol means operated by variations in the rate of flow in said outlet for progressively operating with said valve means to progressively unbalance and balance the pressure on opposite sides thereof and render the stages of the pump active and inactive.

20. A multi-stage centrifugal pump having an inlet and a discharge outlet, an impeller shaft, a plurality of coaxial impellers mounted on said impeller shaft and rotatably driven thereby, a diffuser associated with each impeller and mounted on said impeller shaft for free rotation with respect thereto and for axial movement therealong, each impeller and associated diffuser forming a stage of the pump, and means operable by variation in pressure rise across said inlet and outlet from a predetermined constant pressure rise, to activate or inactivate certain stages of the pump including a servo-control means, means establishing fluid communication from said inlet and said outlet to said servo-control means for operating the same, spring means acting on said servocontrol means and balancing the inlet and outlet pressure thereon, valve means operated by said servo-control means and connected with said inlet, separate fluid passageways connecting said valve means with each diffuser, said valve means being operable to successively connect said passageways from said inlet to said diffusers and balance pressure on said diffusers and accommodate said diffusers to freely rotate, and to relieve inlet pressure from said passageways and unbalance pressure thereon and accommodate movement of said diffusers axially of said shaft, to effect the holding of said diffusers from rotation to render the associated stages of the pump active until balancing of said servo-control means by said spring means.

WILLIAM H. CURTIS.

LESLIE L. ASPELIN.

JAMES C. CARTER.

References Cited in the file of this patent UNITED STATES PATENTS Number Number 10 Number Name 7 Date Baumann Nov. 24, 1931 Algarsson Jan. 3, 1939 Pierce June 11, 1940 De Bolt June 8, 1943 Codrington Jan. 11, 1944 Wilde Oct. '7, 1952 FOREIGN PATENTS Country Date Switzerland May 15, 1945 France Aug. 1, 1919 Germany May 21, 1941 

